ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus PublicationsGöttingen, Germany10.5194/acp-11-11431-2011Interannual variability of ozone and carbon monoxide at the Whistler high elevation site: 2002–2006MacdonaldA. M.1AnlaufK. G.1LeaitchW. R.1ChanE.1TarasickD. W.11Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada1711201111221143111446This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/11/11431/2011/acp-11-11431-2011.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/11431/2011/acp-11-11431-2011.pdf

In spring 2002, an atmospheric measurement site was established at the peak
of Whistler Mountain in British Columbia, Canada to measure trace gases,
particle chemistry and physics, and meteorology. This paper uses continuous
measurements from March 2002 to December 2006 to investigate the influence
of trans-Pacific transport and North American forest fires on both O<sub>3</sub>
and CO at Whistler. Annual mean mixing ratios of O<sub>3</sub> and CO were 41 ppbv
(monthly means of 35–48 ppbv) and 145 ppbv (monthly means of 113–177 ppbv)
respectively with both species exhibiting an annual cycle of late-winter to
early-spring maxima and summer minima. The absence of a broad summer O<sub>3</sub>
peak differs from previously-reported high altitude sites in the western US.
The highest monthly-averaged O<sub>3</sub> and CO mixing ratios relative to the
5-yr monthly means were seen in fall 2002 and spring 2003 with increased
O<sub>3</sub> and CO of 10 % and 25 % respectively. These increases correspond
to anomalously-high values reported at other Northern Hemisphere sites and
are attributed to fires in the Russian Federation. Air mass back trajectory
analysis is used to associate the mean enhancements of O<sub>3</sub> and CO with
trans-Pacific transported or North American air masses relative to the
Pacific background. Mean values of the enhancements for March to June in
trans-Pacific air masses were 6 ppbv and 16 ppbv for O<sub>3</sub> and CO
respectively. In summers 2002–2006, higher CO and O<sub>3</sub> mixing ratios were
almost always observed in North American air masses and this relative
enhancement co-varied for each year with the western US and Canada total
wildfire area. The greatest enhancements in O<sub>3</sub> and CO were seen in
2004, a record year for forest fires in Alaska and the Yukon Territory with
average O<sub>3</sub> and CO mixing ratios 13 and 43 ppbv above background values.